The present invention relates to a method of breaking an aqueous fracturing fluid comprising introducing said aqueous fracturing fluid into contact with an encapsulated viscosity reducing agent said encapsulated viscosity reducing agent comprising an aqueous fluid soluble breaker for said fracturing fluid encapsulated within a membrane comprising a partially hydrolyzed acrylic crosslinked with either an aziridine prepolymer or a carbodiimide, said membrane having an embrittlement effective amount of a micron sized particulate present therein and said membrane having been cured at a temperature of at least about 115xc2x0 F., such that an aqueous fluid in said fracturing fluid can contact said breaker after fracture failure of said membrane to dissolve at least a portion of said breaker and break the fracturing fluid in contact therewith.

1. Field of the Invention
The present invention relates to compositions and methods for treating subterranean formations. Specifically, the invention is directed to compositions used to break fracturing fluids utilized in the stimulation of subterranean formations.
2. Description of the Prior Art
It is common practice to treat subterranean formations to increase the gross permeability or conductivity of such formations by procedures which are identified generally as fracturing processes. For example, it is a conventional practice to hydraulically fracture a well in order to produce one or more cracks or xe2x80x9cfracturesxe2x80x9d in the surrounding formation by mechanical breakdown of the formation. Fracturing may be carried out in wells which are completed in subterranean formations for virtually any purpose. The usual candidates for fracturing, or other stimulation procedures, are production wells completed in oil and/or gas containing formations. However, injection wells used in secondary or tertiary recovery operations, for example, for the injection of water or gas, may also be fractured in order to facilitate the injection of fluids into such subterranean formations.
Hydraulic fracturing is accomplished by injecting a hydraulic fracturing fluid into the well and applying sufficient pressure on the fracturing fluid to cause the formation to break down with the attendant production of one or more fractures. The fracture or fractures may be horizontal or vertical, with the latter usually predominating, and with the tendency toward vertical fracture orientation increasing with the depth of the formation being fractured. Usually a gel, an emulsion or a foam, having a proppant such as sand or other particulate material suspended therein is introduced into the fracture. The proppant is deposited in the fracture and functions to hold the fracture open after the pressure is released and the fracturing fluid flows back into the well. The fracturing fluid has a sufficiently high viscosity to retain the proppant in suspension or at least to reduce the tendency of the proppant to settle out of the fracturing fluid as the fracturing fluid flows along the created fracture. Generally, a gelation agent and/or an emulsifier is used to gel or emulsify the fracturing fluid to provide the high viscosity needed to realize the maximum benefits from the fracturing process.
After the high viscosity fracturing fluid has been pumped into the formation and fracturing of the formation occurred, it is desirable to remove the fluid from the formation to allow hydrocarbon production through the new fractures. Generally, the removal of the highly viscous fracturing fluid is realized by xe2x80x9cbreakingxe2x80x9d the gel or emulsion or, in other words, by converting the fracturing fluid into a low viscosity fluid. Breaking the gelled or emulsified fracturing fluid has commonly been accomplished by adding a xe2x80x9cbreaker,xe2x80x9d that is, a viscosity-reducing agent, to the fracturing fluid prior to pumping into a subterranean formation. However, this technique can be unreliable and sometimes results in incomplete breaking of the fluid and/or premature breaking of the fluid before the fracturing process is complete. Premature breaking can decrease the number or length of fractures obtained and thus, the amount of hydrocarbon recovery. Further, it is known in the art that most fracturing fluids will break if given enough time at an elevated temperature. However, it is, of course, most desirable to return the well back to production as quickly as possible.
It has been demonstrated that the viscosifying polymer in a fracturing fluid is concentrated by a factor of from 5 to 20 times due to fluid loss during pumping and fracture closure. This concentrated polymer generally is referred to as xe2x80x9cfilter cake.xe2x80x9d For example, see G. S. Penney, xe2x80x9cAn Evaluation Of The Effects Of Environmental Conditions In Fracturing Fluids Upon The Long Term Conductivity Of Proppants,xe2x80x9d SPE 16900, presented at the 62nd Annual Technological Conference of SPE, Dallas, Tex., Sep. 27-30, 1987. Further, others have emphasized the effects of filter cake upon conductivity. For example, M. A. Parker and B. W. McDaniel, xe2x80x9cFracturing Treatment Designs Improved By Conductivity Measurements Under In-situ Conditions,xe2x80x9d SPE 16901, presented at the 62nd Annual Technological Conference of SPE, Dallas, Tex., Sep. 27-30, 1987; B. W. McDaniel and M. A. Parker, xe2x80x9cAccurate Design and Fracturing Treatment Refines Conductivity Measurement At Reservoir Conditions,xe2x80x9d SPE 17541, presented at SPE Rocky Mountain Regional Meeting, Casper, Wyo., May 11-13, 1984. An unencapsulated breaker dissolves in the fluid and is lost along with the fluid during fluid loss. The dissolved breaker does not concentrate along with the filter cake concentration of the polymer and thus may not effectively break the filter cake. Therefore, damage to the resulting propped fracture may be permanent unless breaking subsequently occurs due to temperature degradation or dilution with formation fluids.
There have been several proposed methods for the breaking of fracturing fluids which were aimed at eliminating the above problems. For example, U.S. Pat. No. 4,202,795 discloses a method to release a chemical into an aqueous fluid by combining the chemical with a solid hydratable gelling agent and a breaker for the gel formed by the gelling agent when hydrated. The mixture is formed into prills or pellets, preferably having a size and range of from about 20 to about 40 mesh. (U.S. Sieve Series) From combining the pellets with an aqueous fluid into which the chemical is to be released, the gelling agent in the pellets hydrates and forms a protective gel around each of the pellets which prevents the release of the chemical into the aqueous fluid for the time period required for the protective gel to be broken by the gel breaker in the pellets. Once the gel breaker has broken the protective gel, the chemical in the pellets is released into the aqueous fluid. The time required for the protective gel to be broken is varied by varying the quantities of hydratable gelling agent and the gel breaker utilized in the pellets and by using different gelling agents and gel breakers.
U.S. Pat. No. 4,506,734 also provides a method for reducing the viscosity and the resulting residue of an aqueous or oil based fluid introduced into a subterranean formation by introducing a viscosity-reducing chemical contained within hollow or porous, crushable and fragile beads along with a fluid, such as a hydraulic fracturing fluid, under pressure into the subterranean formation. When the fracturing fluid passes or leaks off into the formation or the fluid is removed by back flowing, any resulting fractures in the subterranean formation close and crush the beads. The crushing of the beads then releases the viscosity-reducing chemical into the fluid. This process is dependent upon the closure pressure of the formation to obtain release of the breaker and is thus, subject to varying results dependent upon the formation and its closure rate.
U.S. Pat. No. 4,741,401 discloses a method for breaking a fracturing fluid comprised of injecting into the subterranean formation a capsule comprising an enclosure member containing the breaker. The enclosure member is sufficiently permeable to at least one fluid existing in the subterranean environment or injected with the capsule such that the enclosure member is capable of rupturing upon sufficient exposure to the fluid, thereby releasing the breaker. The patent teaches that the breaker is released from the capsule by pressure generated within the enclosure member due solely to the fluid penetrating into the capsule whereby the increased pressure caused the capsule to rupture, i.e., destroys the integrity of the enclosure member, thus releasing the breaker. This method for release of the breaker would result in the release of substantially the total amount of breaker contained in the capsule at one particular point in time.
In another method to release a breaker, U.S. Pat. No. 4,770,796 teaches or suggests an acid fracturing fluid composition comprising a polymer, a crosslinking agent for said polymer, an aqueous acid and a breaker compound capable of coordinating with titanium or zirconium crosslinking agent. The breaker compound is encapsulated in a composition comprising a cellulosic material and a fatty acid and optionally a wax.
Further, U.S. Pat. No. 4,919,209 discloses a proposed method for breaking a fluid. Specifically, the patent discloses a method for breaking a gelled oil fracturing fluid for treating a subterranean formation which comprises injecting into the formation a breaker capsule comprising an enclosure member enveloping a breaker. The enclosure member is sufficiently permeable to at least one fluid existing in the formation or in the gelled oil fracturing fluid injected with the breaker capsule, such that the enclosure member is capable of dissolving or eroding off upon sufficient exposure to the fluid, thereby releasing the breaker.
U.S. Pat. No. 5,164,099 discloses a proposed method for breaking a fluid utilizing a percarbonate, perchlorate or persulfate breaker encapsulated with a polyamide. The polyamide membrane is permeable to at least one fluid in the formation which dissolves the breaker and the breaker then diffuses through the membrane to break the fracturing fluid with the membrane staying intact during the breaker release.
U.S. Pat. No. 5,373,901 discloses a method for breaking a viscosified fluid utilizing an aqueous soluble breaker encapsulated within a membrane comprising a partially hydrolyzed acrylic crosslinked with either an aziridine prepolymer or a carbodiimide. The membrane has imperfections through which an aqueous fluid can diffuse inwardly through the membrane to dissolve at least a portion of the breaker and then diffuse outwardly from the encapsulated breaker to contact and break the fracturing fluid with the membrane staying intact during the breaker release. The imperfections can be created in the membrane by the addition of particulate material such as silica to the coating during the formation of the membrane coating.
PCT Application WO 99/61747 discloses a method for breaking a fluid utilizing a breaker encapsulated within a hydrolytically degradable polymer coating. The hydrolytically degradable polymer reacts with the water to chemically break down the coating to predominately non-solid components in a time and temperature range appropriate for the intended use. A preferred polymer coating is poly (alkyl-2-cyanoacrylate).
There remains a need for a method for the controlled breaking of fracturing fluids which is more economical, minimizes breaker loss during fluid loss to the formation and provides not only controlled release of the breaker, but also reduces damage to the formation and facilitates well clean-up.
The present invention relates to a method for controllably breaking an aqueous based fracturing fluid utilized to stimulate a subterranean formation. The present invention is further directed to an encapsulated viscosity reducing agent which is capable of providing controlled release at elevated pH in aqueous-based fracturing fluids. The encapsulated viscosity reducing agent comprises agglomerated particles of a viscosity reducing agent, which may also be referred to as a breaker, enclosed within an inert membrane that is subject to brittle fracture when exposed to subterranean formation closure pressure whereby the formation fluids may contact the viscosity reducing agent after membrane failure to dissolve the viscosity reducing agent in the membrane into the fracturing fluid. The fracturable membrane stays substantially intact until the period of release of the breaker, thereby providing controlled release.
Using the method of the present invention there is provided a means of controllably releasing amounts of a breaker within a proppant pack within a subterranean formation. The present method provides an encapsulation membrane which is capable of functioning in an aqueous based fluid at temperatures of from 60xc2x0 F. to about 300xc2x0 F. and at a fluid pH of up to at least about 12 without premature release of the breaker into the fluid.
The method and composition of the present invention provides a means of breaking an aqueous linear or crosslinked fracturing fluid used to stimulate a subterranean formation.
The crosslinked aqueous fracturing fluid is prepared by hydrating a polymer such as guar, hydroxyalkylguar, hydroxyalkylcellulose, carboxyalkylhydroxyguar, carboxyalkylhydroxyalkylguar, cellulose or other derivatized cellulose, xanthan and the like in an aqueous fluid to which is added a suitable crosslinking agent. Suitable crosslinking agents include compounds such as borates, zirconates, titanates, pyroantimonates, aluminates and the like. Generally, the encapsulated breaker of the present invention can be added to any aqueous fracturing fluid generally known in the art. In the practice of the present invention the encapsulated breaker can be injected with the fracturing fluid or, if added to a carrier fluid, injected into a subterranean formation prior to, simultaneously with or subsequent to injection of the fracturing fluid. Generally, the encapsulated breaker will be admixed with fracturing fluid and a proppant material prior to introduction into the subterranean formation. If a carrier fluid is utilized, it can comprise substantially any of the aqueous liquids utilized to form fracturing fluids.
The encapsulated breaker of the present invention is made using known microencapsulation techniques. The encapsulated breaker can be made utilizing a fluidized bed process. One version of this method is referred to as the Wxc3xcrster process and a modification of such process utilizes a top spray method. Equipment to effect the coating is available from, for example, Glatt Air Techniques, Inc. Ramsey, N.J.
The breaker which is enclosed by the encapsulant can be substantially any material which does not adversely interact or chemically react with the encapsulation coating to destroy its utility. The breaker material can comprise, for example, enzymes such as hemicellulase on an inert substrate, oxiders such as sodium or ammonium persulfate, organic acids or salts, such as citric acid or a citrate, fumaric acid, liquids adsorbed on a solid substrate, solid perborates, solid peroxides or other oxidizers, mixtures of two or more materials and the like.
The encapsulating material comprises a partially hydrolyzed acrylic, preferably in an aqueous based form which is crosslinked with either an aziridine prepolymer or a carbodiimide. More particularly, the term partially hydrolyzed acrylic as used herein means any of the vinyl acrylic latex polymers containing from about 0-60% by weight monovinyl aromatic content as styrene, from about 5-25% by weight alpha, beta unsaturated carboxylic acid content and from about 15-95% by weight alkyl acrylate or methacrylate ester content. The unsaturated carboxylic acid can comprise, for example, acrylic acid or methyl acrylic acid or mixtures thereof. The alkyl acrylate or methacrylate ester can comprise, for example ethyl butyl or 2-ethylhexyalacrylate, methyl, butyl or isobutyl methacrylate or mixtures thereof. The vinyl acrylic latex polymers are stabilized by the addition of appropriate nonionic or anionic/nonionic surfactant systems in accordance with well-known methods for preparing and stabilizing latex polymer systems. Vinyl acrylic latex polymers of the type described above are commercially available from, for example, Rohm and Haas Company, Philadelphia, Pa. or S. C. Johnson Wax, Racine, Wis.
The aziridine prepolymer can comprise, for example, pentaerythritol-tris-[xcex2-(aziridinly) propionate]. The carbodiimide can comprise, for example, 1,3-dicyclohexylcarbodiimide.
The partially hydrolyzed acrylic encapsulating material is admixed with a particulate micron sized material such as silica prior to or simultaneously with coating of the breaker. The acrylic is admixed with the particulate silica in an amount such that the particulate comprises from about 20 to about 80 percent by weight of coating solids present. Preferably, the silica comprises from about 50 to about 70% by weight of coating solids present. The particulate silica can have a size range of from about 1 micron to about 15 microns. Preferably the silica has a median particle size of from about 2 to about 3 microns and preferably contains less than 33 percent, by weight, sub-micron sized particles. The presence of substantial quantities of sub-micron sized particles has been found to adversely effect the performance of the encapsulated breaker of the present invention resulting in unregulated release of large quantities of breaker after exposure to a fracturing fluid.
The crosslinking agent is admixed with the partially hydrolyzed acrylic and silica in an amount of from about 1 to about 5 percent by weight of total coating solids present. Preferably, the crosslinking agent is present in an amount of from about 2.5 to 3.5 percent by weight of total coating solids.
When utilized in a fluidized bed coating process the encapsulated breaker coating is advantageously utilized in the form of an aqueous or solvent-based solution or dispersion which sometimes may be referred to as a latex which may contain from about 40 to about 60 percent by weight solids to facilitate spray coating of the breaker. Preferably the encapsulated breaker will have an encapsulant coating in an amount of from about 6 to about 70 percent by weight of the encapsulated breaker. Most preferably, the coating will comprise from about 35 to about 55 percent by weight of the encapsulated breaker depending upon the rate of release desired.
In the practice of the present invention, depending upon the temperature of the formation to be treated and the desired break time of the fracturing fluid, the encapsulated breaker may be present in an amount of from about 0.1 to in excess of 50 pounds per 1000 gallons of fracturing fluid. The encapsulated breakers of the present invention also may be utilized in a fracturing fluid with quantities of unencapsulated breakers, depending upon the specific break time desired.
As previously indicated, the encapsulated breakers are made by well known fluidized bed encapsulation techniques wherein the particles of breaker are sprayed with the encapsulant while suspended in a flow of air or other gas within a spray chamber. To maintain product uniformity with respect to performance, prior to encapsulation of the breaker material, the breaker preferably is sized to remove a substantial portion of any fines or clumps of breaker particles and provide a starting material with a particle size of from about 100 to 900 xcexcm. In this manner, the subsequently prepared agglomerated encapsulated breaker will have, within a relatively narrow range, generally similar breaker release control properties. Generally, the encapsulated breaker is prepared by forming agglomerates of the breaker having a membrane coating of the crosslinked partially hydrolyzed acrylic and silica emulsion coating mixture of a certain average percentage to obtain the desired controlled release of the breaker for a particular fracturing fluid. The quantity of and size of the particulate silica present in the sprayed coating will significantly affect the permeability of the membrane created. The size of the agglomerated encapsulated breaker particles varies depending upon the desired amount of breaker to be released and the desired rate at which the breaker is to be released. Preferably, the agglomerates have an average particle size of from about 1 to 3 mm and most preferably about 1.25 to 2.5 mm. This however can be modified by changing the operating conditions during the coating process. Generally, it is preferred that the size of the agglomerated encapsulated breaker particles should be close to or slightly larger than that of the proppant, if any, present in the fracturing fluid. This further minimizes any formation damage that may result from introduction of the fracturing fluid into a subterranean formation. However, it is to be understood that particles having a size smaller than the proppant also may be utilized.
In the present invention, the breaker encapsulated within the coating membrane is primarily released from within the membrane by brittle fracture failure of the agglomerate coating. Fluid, upon fracture failure of the membrane, contacts the core of the particle whereupon it dissolves the breaker. The released breaker solution contacts the fracturing fluid whereupon it subsequently breaks the fracturing fluid.
The addition of the in-excess-of one micron mean diameter particles to the partially hydrolyzed acrylic coating causes the coating to be more brittle to facilitate the fracture failure release process. While the specific description set forth hereinabove has referred to particulate silica as the particulate additive to the coating, it is believed that any inert particulate of a similar particle size also could be utilized. The silica merely represents one commercially available preferred material. Examples of other suitable particulates would include calcium carbonate, titanium dioxide, barium sulfate and calcium sulfate or the like.
After formation of the coated agglomerates of the encapsulated breaker material, the encapsulated breaker preferably is subjected to a period of elevated temperature to further cure the membrane coating. Preferably, the membrane coating is cured at a temperature of from about 115xc2x0 F. to about 145xc2x0 F. for from about 1 hour to several days before use of the breaker. The elevated temperature curing has been found to improve the release rate of the breaker upon crushing of the material in the formation and assist in preventing early release prior to the desired release time within the formation.
The encapsulated breaker of the present invention has been surprisingly discovered to exhibit effective release rate control at pH""s above 7. The release rate control is believed to result from the use of the crosslinker with the partially hydrolyzed acrylic. The crosslinking process is believed to prevent or assist in minimizing the caustic xe2x80x9cswellingxe2x80x9d of acrylics which is well known to those individuals skilled in the art of applying acrylic-type film coatings. The crosslinked coating has been found to effectively control the rate of release of the breaker when contained in an aqueous fracturing fluid having a pH of from about 2 to about 12.
The controlled release of the breaker from the encapsulated breaker of the present invention is effected without substantial leaching of the breaker through the membrane prior to the period in which a majority of the breaker is released. The breaker is released either by contact with the aqueous fluid contained in the fracturing fluid or any other aqueous fluid which may contact the encapsulated breaker after brittle fracture failure of the membrane within the subterranean formation or wellbore penetrating the formation.

Encapsulated breakers and method for use in treating subterranean formations


The invention relates to devices including rotary units and rotary mechanisms that are suitable for use in numerous applications. Rotary units typically include rotational components that are configured to rotate. In some embodiments, for example, multiple rotary units are assembled in rotary mechanisms such that neighboring pairs of rotational components counter-rotate or contra-rotate relative to one another during operation of the rotary mechanisms. Rotational components generally include one or more implements that are structured to perform or effect one or more types of work as the rotational components rotate relative to one another in a given rotary mechanism. In certain embodiments, implements are configured to rotate and/or to effect the movement of other components as rotational components rotate.

In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric current to flow through an external circuit. The source of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air, or any other source of mechanical energy. Generators provide nearly all of the power for electric power grids.
The reverse conversion of electrical energy into mechanical energy is done by an electric motor, and motors and generators have many similarities. Many motors can be mechanically driven to generate electricity and frequently make acceptable generators.

Apparatus comprising counter-rotational mechanisms and related methods to convey current


A portable light unit for treatment of seasonal affective disorders. The portable device is carried in a small case having four bulbs capable of emitting full spectrum light at 10,000 lux intensity for each therapy session. Therefore, the device can be carried by the patient or the physician to the patient.

1. Field of the Invention
The present invention relates generally to an illumination device. More specifically, the invention is a portable briefcased illumination device for treatmemt of seasonal affective disorders.
2. Description of the Related Art
The relative art of interest describes various illumination devices, but none discloses the present invention. There is a need for a portable illumination device adapted to treat seasonal affective syndromes and disorders.
The related art will be discussed in the order of perceived relevance to the present invention.
U.S. Pat. No. 5,149,184 issued on Sep. 22, 1992, to Philip Hughes et al. describes a combined work station and phototherapy unit in which the light source is cantilevered at adjustable angles on a rotatable flat lid containing a plurality of fluorescent tubes and ballasts behind a diffuser panel. A switching arrangement can turn on two lamps (3,300 lux), four lamps (6,600 lux) or six lamps (10,000 lux) via a power cord. The work stations can vary in size from 2 ft. square, 1 ft. by 3 ft. and 10 inches by 3 ft. The work station is distinguishable for its limitation to a large boxed unit with a cantilevered illuminating panel.
U.S. Pat. No. 5,919,217 issued on Jul. 6, 1999, to Philip C. Hughes describes a portable therapy light housed in a rectangular box of molded plastic having a cutout for the eyes and an bridge for resting the device on the patient""s nose. Two side arms for, the ears are also provided. The illumination source is either a twin-tubed fluorescent lamp or a single incandescent lamp powered 10 by either A.C. voltage or batteries. The device is distinguishable for its boxed eyeglass type structure with conventional illumination sources.
U.S. Pat. No. 5,447,527 issued on Sep. 5, 1995, to Murray M. Waldman describes a therapeutic light device comprising a light bulb in a light fixture emitting only a wavelength of 490-520 nanometers and restricting the light energy radiance to between 1.8 to 200 microwatts per square centimeter over the eyes of the patient. The light restricting apparatus can be a narrowband light transmission filter placed strategically over the upper portion or the phosphor of a fluorescent bulb. The device is distinguishable for its restrictive light tolerance, two-part illumination and the use of a fluorescent light source.
U.S. Pat. No. 5,197,941 issued on Mar. 30, 1993, to Barbara Whitaker describes a portable device for controlling circadian rhythm disorders comprises the following components in a plastic molded box having a curved lid with an undefined reflective concave surface and an external ion generator connected by an extension cord. The box contains a fluorescent lamp energized by either 120 volts A.C. or an integrated battery. A progammable microprocessor controls a liquid crystal clock display module and a speaker. On/off control switches include a sleep function switch, an override switch for lamp control, a switch for the ion generator, and a volume control for the speaker. The device is distinguishable for its manifold features limited to a single fluorescent lamp.
U.S. Pat. No. 4,911,166 issued on Mar. 27, 1990, to Stephen B. Leighton et al. describes a portable light delivery system using a point source of light from a high intensity halogen or incandescent bulb and directing a large fraction of the light directly into the patient""s eyes without focusing the light to my cause visual damage. A helmet has two anchored assemblies suspended in front of the patient. Each light assembly has a light source bouncing its illumination from a concave mirror rear wall to a positive convex lens. The device is distinguishable for its reliance on a pair of suspended light sources with a frontal lens.
U.S. Pat. No. 5,562,719 issued on Oct. 8, 1996, to Marcelo E. Lopez-Claros describes a light therapy apparatus comprising a mask which provides illumination by adjustably dividing the visual field of each eye into temporal and nasal visual fields by internal walls. The two individual sources of illumination are fluorescent light bulbs having an intensity of 2,500 to 10,000 lux. The apparatus is distinguishable for its required segmented aspect for illumination of each eye.
U.S. Pat. No. 5,824,024 issued on Oct. 20, 1998, to Daniel C. Dial describes illumination devices for treating light deficiency and mood disorders including color therapy. The illumination fixture contains a convoluted arrangement of neon gas and mercury containing tubing and optionally with optic cables. The rectangular light reflecting back surface is white plexiglass. The device is distinguishable for its requirement for fluorescent lighting arranged in a convoluted pattern.
W.I.P.O. Patent Application No. WO 89/08475 published on Sep. 21, 1989, for George C. Brainard describes a portable phototherapeutic device incorporated in a cap to emit at least 200 lux light on the eyes of the wearer. The preferred embodiment employs a conical canopy to focus the light from a quartz halogen lamp positioned in front and controlled by a rheostat control located on the side of the cap for obtaining a preferred 2,000 to 2,500 lux intensity. A battery pack is housed under the cap in the rear. A second embodiment employs the batteries under the top of the hat and suspends the lamp underneath an extension. A third embodiment poaitions the lamp above a rectangular radiation shield. A fourth embodiment employs a lamp above the visor of a sun visor cap and a remote control wired to the lamp. The devices are distinguishable for their restriction to caps having a quartz halogen lamp.
W.I.P.O. Patent Application No. WO 96/14899 published on May 23, 1996, for Optomed Opto Medical Systems GMBH describes a light therapy device comprising fluorescent lamps of different mono-chromatic radiation used in combination with a prior application of a light-sensitizing ointment. The device is distinguishable for its requirement for fluorescent lamps of different monochromatic radiation.
German Patent Application No. DE 44 33 291 A1 published on Mar. 21, 1996, for Hans-Jurgen Hentschel describes as best understood a rectangular light box containing at least four daylight lamps in individual apertured concave reflector elements with the apertures aligned with slits in the rear of the box. The front of the box is closed with a glass pane. The light box is distinguishable for its individual lamp reflecting surfaces.
German Patent Application No. 198 36 312 A1 published on Feb. 24, 2000, for Hans-Peter Reuter describes a lamp having a spectrum corresponding to natural daylight comprising three fluorescent light tubes behind a housing which includes a plurality of elongated hollow (triangular in cross-section) reflector elements having colored surfaces which match the spectrum of the light sources. A microprocessor is included. The lamp is distinguishable for its unique lamp and reflector structure and microprocessor control.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus, a portable light unit for treatment of seasonal affective disorders solving the aforementioned problems is desired.
The present invention is directed to a portable illumination device for the treatment of seasonal affective disorders. The portable device is carried in a small hard covered case having four bulbs capable of emitting full spectrum light at 10,000 lux intensity for each therapy session. Therefore, the device can be carried by the patient or the physician to the patient.
Accordingly, it is a principal object of the invention to provide a portable illumination device.
It is another object of the invention to provide a portable illumination device capable of treating seasonal affective disorders.
It is a further object of the invention to provide a portable illumination device capable of treating seasonal affective disorders having four bulbs capable of emitting full spectrum light at 10,000 lux intensity for each therapy session.
Still another object of the invention is to provide a portable illumination device capable of treating seasonal affective disorders carried in a hard covered briefcase having a rear mirror.
It is an object of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.
These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.

Portable light unit for treatment of seasonal affective disorders


The present invention relates to photographic elements, including photographic prints, having a protective overcoat that resists fingerprints, common stains, and spills. More particularly, the present invention provides a processing-solution-permeable protective overcoat that is water resistant in the final processed product and which, at the same time, provides improved wet-abrasion resistance.

The present invention relates to a method of post-development hardening of aqueous swellable binders underlying a relatively nonswellable protective overcoat of a photographic element. The invention also relates to a photographic element providing both water-resistance and improved wet-abrasion resistance.
Silver halide photographic elements contain light sensitive silver halide in a hydrophilic emulsion. An image is formed in the element by exposing the silver halide to light, or to other actinic radiation, and developing the exposed silver halide to reduce it to elemental silver.
In color photographic elements, a dye image is formed as a consequence of silver halide development by one of several different processes. The most common is to allow a by-product of silver halide development, oxidized silver halide developing agent, to react with a dye forming compound called a coupler. The silver and unreacted silver halide are then removed from the photographic element, leaving a dye image.
In either case, formation of the image commonly involves liquid processing with aqueous solutions that must penetrate the surface of the element to come into contact with silver halide and coupler. Thus, gelatin, and similar natural or synthetic hydrophilic polymers, have proven to be the binders of choice for silver halide photographic elements. Unfortunately, when gelatin, and similar polymers, are formulated so as to facilitate contact between the silver halide crystal and aqueous processing solutions, they are not as tough and mar-resistant as would be desired for something that is handled in the way that an imaged photographic element may be handled. Thus, fingerprints can easily mark the imaged element, it can be scratched or torn and it can swell or otherwise deform when it is contacted with liquids.
There have been attempts over the years to provide protective layers for gelatin based photographic systems that will protect the images from damages by water or aqueous solutions. U.S. Pat. No. 2,173,480 describes a method of applying a colloidal suspension to moist film as the last step of photographic processing before drying. A series of patents describes methods of solvent coating a protective layer on the image after photographic processing is completed and are described in U.S. Pat. Nos. 2,259,009, 2,331,746, 2,798,004, 3,113,867, 3,190,197, 3,415,670 and 3,733,293. U.S. Pat. No. 5,376,434 describes a protective layer formed on a photographic print by coating and drying a latex on a gelatin-containing layer bearing an image. The latex is a resin having a glass transition temperature of from 30xc2x0 C. to 70xc2x0 C. The application of UV-polymerizable monomers and oligomers on processed image followed by radiation exposure to form crosslinked protective layer is described in U.S. Pat. Nos. 4,092,173, 4,171,979, 4,333,998 and 4,426,431. One drawback for the solvent coating method and the radiation cure method is the health and environmental concern of those chemicals to the coating operator. The other drawback is that these materials need to be coated after the processing step. Thus, the processing equipment needs to be modified as well as the personnel running the processing operation need to be trained. In addition, several lamination techniques are known and practiced in the trade.
U.S. Pat. Nos. 3,397,980, 3,697,277 and 4,999,266 describe methods of laminating polymeric sheet film on the processed image as the protective layer. U.S. Pat. No. 5,447,832 describes the use of a protective layer containing a mixture of high and low Tg latices as the water-resistant layer to preserve the antistat property of the V2O5 layer through photographic processing. This protective layer is not applicable to the image formation layers since it will detrimentally inhibit the photographic processing. U.S. Pat. No. 3,443,946 provides a roughened (matte) scratch-protective layer, but not a water-impermeable one. U.S. Pat. No. 3,502,501 provides protection against mechanical damage only; the layer in question contains a majority of hydrophilic polymeric materials, and must be permeable to water in order to maintain processability. U.S. Pat. No. 5,179,147 likewise provides a layer that is not water-protective. However, all these techniques need to be carried out after the image has been formed, which adds a large cost to the final imaged product.
Protective coatings that need to be applied to the image after it is formed, several of which were mentioned above, adds a significant cost to the final imaged product. A number of patents have been directed to water-resistant protective coatings that can be applied to a photographic element prior to development. For example, U.S. Pat. No. 2,706,686 describes the formation of a lacquer finish for photographic emulsions, with the aim of providing water- and fingerprint-resistance by coating the light-sensitive layer, prior to exposure, with a porous layer that has a high degree of water permeability to the processing solutions. After processing, the lacquer layer is fused and coalesced into a continuous, impervious coating. The porous layer is achieved by coating a mixture of a lacquer and a solid removable extender (ammonium carbonate), and removing the extender by sublimation or dissolution during processing. The overcoat as described is coated as a suspension in an organic solvent, and thus is not desirable for large-scale application. More recently, U.S. Pat. No. 5,853,926 to Bohan et al. discloses a protective coating for a photographic element, involving the application of an aqueous coating comprising polymer particles and a soft polymer latex binder. This coating allows for appropriate diffusion of photographic processing solutions, and does not require a coating operation after exposure and processing. Again, however, the hydrophobic polymer particles must be fused to form a protective coating that is continuous and water-impermeable.
U.S. Pat. No. 5,856,051 describes the use of hydrophobic particles with gelatin as the binder in an overcoat formulation. This invention demonstrated an aqueous coatable, water-resistant protective overcoat that can be incorporated into the photographic product, allows for appropriate diffusion of photographic processing solutions, and does not require a coating operation after exposure and processing. The hydrophobic polymers exemplified in U.S. Pat. No. 5,856,051 include polyethylene having a melting temperature (Tm) of 55 to 200xc2x0 C., and therefore capable of forming a water-resistant layer by fusing the layer at a temperature higher than the Tm of the polymer after the sample has been processed to generate the image. The coating solution is aqueous and can be incorporated in the manufacturing coating operation without any equipment modification. The fusing step is simple and environmentally friendly to photofinishing laboratories. Since the particles are incorporated entirely within the uppermost layer, this approach does not suffer from a lack of mechanical strength and integrity during transport and handling prior to image formation and fusing. However, the scratch resistance of such an overcoat after fusing is a serious concern, since polyethylene is a very soft material.
Similarly, commonly assigned U.S. Ser. No. 09/353,939 and U.S. Ser. No. 09/548,514, respectively, describe the use of a polystyrene-based material and a polyurethane-based material, with gelatin as the binder, in an overcoat for a photographic element, which overcoat can be fused into a water resistant overcoat after photographic processing is accomplished to generate an image. Finally, U.S. Ser. No. 09/548,514 describe the use of epoxy materials in the overcoat with gelatin as the binder, which similar to polyethylene, polystyrene and polyurethane can be fused into a water resistant overcoat after photographic processing is completed.
Commonly assigned U.S. Ser. No. 09/235,436 discloses the use of a processing solution permeable overcoat that is composed of a urethane-vinyl copolymer having acid functionalities. Commonly assigned U.S. Ser. No. 09/235,437 and U.S. Ser. No. 09/448,213 disclose the use of a second polymer such as a gelatin or polyvinyl alcohol to reduce such defects and disadvantages.
A problem with these photographic elements, which have overcoats provided at the point of manufacture (and hence must be permeable to aqueous solutions during the processing step) is that the post-process photographic element with a water/stain resistant overcoat may exhibit unsatisfactory abrasion resistance in the wet state. In particular, if allowed to come into contact with aqueous solutions for a sufficient length of time such that the underlying hydrophilic layers can swell, the photographic element becomes prone to abrasion when wiped with a dry cloth or paper towel. Therefore, there is a need to improve the wet abrasion resistance of the imaged element bearing the aforementioned water resistant protective overcoat.
The present invention is directed to a method of processing a photographic element containing a processing-solution permeable overcoat overlying an aqueous swellable photographic layer comprising at least one hydrophilic binder, which method includes treating the photographic element, during or after development, with at least one hardening agent for the swellable binder, so that the swellability of the photographic layer relative to the overcoat is lowered. The photographic element, after processing, comprises a water resistant protective overcoat that exhibits very good wet abrasion resistance.
The present invention is also directed to a processed photographic element containing the final image, comprising a water-resistant protective overcoat overlying the imaged layers, wherein the photographic element has been hardened during or after development such that the Swell Ratio of the photographic element is less that 0.9, wherein the Swell Ratio is defined as the Equilibrium Swell of the photographic element after the hardening of step (d) divided by the Equilibrium Swell of an identical photographic element without the hardening in step (d). Preferably, the Swell Ratio is less than about 0.8, more preferably 0.1 to 0.8. Thus, the swellability of the photographic element is decreased by at least 10%, preferably at least 20% after development is completed compared to prior to development.
The present invention provides an improved imaged photographic element (processed photographic element), such as a photographic print comprising a water-resistant overcoat, which imaged photographic element exhibits improved wet abrasion resistance. The present invention is also directed to a method of making the imaged photographic element by the use of a post-development hardener for treating the one or more image layers underlying the overcoat layer of an imaged photographic element. In accordance with the invention, the aqueous swellable binder in the image layers underlying the relatively nonswellable overcoat of the imaged element is hardened after exposure but during or after development of the image (not before development).
In one particular embodiment, a photographic element having at least one silver halide light-sensitive emulsion layer and a protective overcoat is treated after processing with a hardener for gelatin, and the overcoat layer comprises a pH switchable polymer, a crosslinker for the polymer, and a second polymer that is water soluble. This particular overcoat allows excellent permeability of the developer solution at pH greater than 7 during development of the silver halide light sensitive emulsion layer to provide an imaged photographic element.
In another embodiment of the invention, the overcoat may comprise a hydrophobic porous matrix containing a hydrophilic dispersed phase or hydrophobic polymeric particles in a soluble (or solubilizable) hydrophilc matrix. The polymer overcoat may be further coalesced into a continuous hydrophobic material by fusing (heat and/or pressure) if needed after processing to form a water-resistant or water impermeable protective overcoat with excellent gloss characteristics. Fusing, which depending on the overcoat, may be optional is preferably done at a temperature from 25 to 200xc2x0 C.
Various hardening agents may be employed in the practice of this invention to obtain the necessary Swell Ratios. Many conventional hardeners are known, for example, to crosslink gelatin. Representative gelatin crosslinking agents useful in the present invention are illustrated, but not limited, by the following structures:
I. Aldehyde and Related Compounds:
II. Pyridiniums:
wherein X=BF4xe2x88x92, CF3SO3xe2x88x92, PF6xe2x88x92, Halide.
III. Olefins:
IV. Carbodiimides:
V. Epoxides:
wherein linking groups L1 and L2 are each independently a single bond, a carbon atom, an oxygen atom, a sulfur atom, a carbonyl group
a carboxylic ester group
a carboxylic amide group
a sulfonyl group
a sulfonamide group
an ethyleneoxy group, a polyethyleneoxy group, or an amino group
wherein substituents X, Y, and Z are each independently a hydrogen atom or an alkyl group of 1-4 carbon atoms; and
wherein R1 and R2 are each independently a hydrogen atom, a substituted or unsubstituted, linear or branched, saturated or unsaturated alkyl group of 1 to 10 carbon atoms (such as methyl, ethyl, n-propyl, isopropyl, t-butyl, hexyl, decyl, benzyl, methoxymethyl, hydroxyethyl, iso-butyl, and n-butyl), a substituted or unsubstituted aryl group of 6 to 14 carbon atoms (such as phenyl, naphthyl, anthryl, tolyl, xylyl, 3-methoxyphenyl, 4-chlorophenyl, 4-carbomethoxyphenyl and 4-cyanophenyl), a substituted or unsubstituted cycloalkyl group of 5 to 14 carbon atoms such as cyclopentyl, cyclohexyl, and cyclooctyl), a substituted or unsubstituted, saturated or unsaturated heterocyclic group (such as pyridyl, primidyl, morpholino, and furanyl), a cyano group, or a solubilizing group such as a carboxylic acid group, a sulfonic acid group, a phosphonic acid group, a hydroxamic acid group, a sulfonamide group, and a hydroxy group (and their corresponding salts). Examples of suitable substituents for R1 and R2 include one or more sulfonate groups, sulfate groups, carboxy groups, hydroxy groups, phosphonic acid groups, hydroxamic acid groups, amine groups, amide groups, ester groups, sulfonamide groups, nitro groups, cyano groups, oxo groups, and halogen atoms. Preferably, at least one of R1 and R2 is or contains a solubilizing group that-becomes negatively charged when ionized, such as an acidic group. Examples of these solubilizing groups include, but are not limited to, carboxylic acid, sulfonic acid, phosphonic acid, hydroxamic acid, sulfonamide, and hydroxy groups (and their corresponding salts). One or more of R1 and R2 also may be, or may contain, a polyethylenoxy group. R1 and R2 may be joined by sufficient numbers of carbon, nitrogen, and sulfur atoms to form, independently, a five- or six-membered ring. When L is linked to a ring structure, it could be single or multiple substitutions.
More specific representative examples of hardening agents are represented by the following structures:
I. Aldehyde and Related Compounds:
II. Pyridiniums:
III. Olefins:
IV. Carbodiimides:
V. Epoxides:
VI. Triazines:
These compounds can be readily prepared using the published synthetic procedure or routine modifications that would be readily apparent to one skilled in the art of synthetic organic chemistry.
Other examples of hardening agents can be found in standard references such as The Theory of the Photographic Process, T. H. James, Macmillan Publishing Co., Inc. (New York 1977) or in Research Disclosure, September 1996, Number 389, Part IIB (hardeners). Research Disclosure is published by Kenneth Mason Publications, Ltd., Dudley House, 12 North St., Emsworth, Hampshire P010 7DQ, England. Organic hardening agents are preferred over inorganic hardeners.
The imaged photographic element contains at least one imaged layer containing image dye (derived from the reaction of the original silver-halide with dye-forming coupler in the emulsion) and comprises at least one binder or vehicle that can be hardened according to the present invention. Useful binders include naturally occurring substances such as proteins, protein derivatives, gelatin (e.g., alkali-treated gelatin such as cattle bone or hide gelatin, or acid treated gelatin such as pigskin gelatin), and gelatin derivatives (e.g., acetylated gelatin, phthalated gelatin, and the like). Also useful as vehicle extenders are hydrophilic water-permeable colloids. These include synthetic polymeric peptizers, carriers, and/or binders such as poly(vinyl alcohol), poly(vinyl lactams), acrylamide polymers, polyvinyl acetals, polymers of alkyl and sulfoalkyl acrylates and methacrylates, hydrolyzed polyvinyl acetates, polyamides, polyvinyl pyridine, methacrylamide copolymers, and the like.
In the case of gelatin as the vehicle, gelatin crosslinking agents (as the hardener) are included in a processing solution in an amount of at least about 0.01 wt. % and preferably from about 0.1 to about 10 wt. %. More than one gelatin crosslinking agent can be used in the rinse solution if desired.
In one embodiment of the invention, the hardening agent may be included in a rinse solution following the developing solution. Alternatively, it is also possible to have the hardening agent in the developing solution, so long as the hardening is less rapid than the development or is completed after the development is substantially or essentially completed.
In still other embodiments of the invention, the hardening agent can be contained in a blocked form in the photographic layer, which blocked form is released during development or later, for example, by high alkalinity. Examples of blocking groups for hardeners can be found in the prior art. Alternatively, one or more hardening agents may be contained in a separate layer from the imaging layer, whereby the hardening agents are released and/or migrate to the photographic layer during or after development of the image.
In one preferred embodiment of the invention, in which the primary binder is gelatin, the hardening agent is applied to the imaged element in the form of a rinse solution. The pH of the rinse solution is generally not adjusted after the addition of gelatin crosslinking agent and it could be either acidic or alkaline depending on the choice of the crosslinking agent. However, certain buffer solution can be used, if desired, to control the pH of the rinse solution. Particularly useful buffers include, but are not limited to, carbonates, borates, tetraborates, phosphates, glycine salts, leucine salts, valine salts, proline salts, alanine salts, aminobutyric acid salts, lycine salts, guanine salts and hydroxybenzoates.
The support material used with this invention can comprise various polymeric films, papers, glass, and the like. The thickness of the support is not critical. Support thicknesses of2 to 15 mils (0.002 to 0.015 inches) can be used.
One type of coating composition that can be employed for forming a protective overcoat layer in accordance with the present invention comprises a continuous aqueous phase having therein a film forming binder, wherein the binder comprises hybrid urethane-vinyl copolymer having an acid number of greater than or equal to 5 and less than or equal to 30. Acid number is in general determined by titration and is defined as the number of milligrams of potassium hydroxide (KOH) required to neutralize 1 gram of the polymer. Another type of copolymer that can be used are polyester ionomers, disclosed in commonly assigned U.S. Ser. No. 09/588,960. Other types of overcoats that are designed to be process-permeable during development and water-resistant after development comprise a hydrophobic porous matrix or membrane as disclosed in U.S. Ser. No. 09/464,949, or comprise hydrophobic particles contained in a gelatin matrix, as disclosed in U.S. Ser. No. 09/547,374. Still other such overcoats comprise polymeric particles that employ fusing after development to close pores in the overcoat that exist during development, such as disclosed in U.S. Ser. No. 09/313,555, U.S. Ser. No. 09/353,939, and U.S. Ser. No. 09/548,514. Still other types of overcoats are contemplated. However such overcoats all have in common the fact that they are permeable to the water and developing solutions during development and become water resistant (but not completely water impermeable) in the final product. The use of the hardening agent to harden the underlying layers prevents any water that manages to soak through the overcoat from swelling. This can happen, even if the overcoat is water-resistant, if an aqueous solution such as punch or other such household commodity, is allowed to remain in contact with the imaged element for an extended period of time. For example, a print may be inadvertently laid on a wet spot on a table. It has been found that abrasion can potentially occur when the wet print is discovered and an attempt is made to dry the print, for example, by using a paper towel. In such circumstances, scratches can occur on the overcoat due to swelling of the underlying material and the resultant stress on the relatively non-swellable and non-healing overcoat. This phenomenon can be significantly reduced by means of the present invention. In contrast, if the imaged element did not have the water-resistant overcoat, such wet abrasion is not such a problem since the swollen layer could then heal. Merely drying the non-water-resistant print may suffice to return the print to its original state without damage.
The polymer overcoat should be clear, i.e., transparent, and preferably colorless. But it is contemplated that the polymer overcoat can have some color for the purposes of color correction, or for special effects, so long as it does not detrimentally affect the formation or viewing of the image through the overcoat. Thus, there can be incorporated into the polymer, dye that will impart color. In addition, additives can be incorporated into the polymer that will give the overcoat, desired properties. For example, a UV absorber can be incorporated into the polymer to make the overcoat UV absorptive, thus protecting the image from UV induced fading. Other additional compounds may be added to the coating composition, depending on the functions of the particular layer, including surfactants, emulsifiers, coating aids, lubricants, matte particles, rheology modifiers, crosslinking agents, antifoggants, inorganic fillers such as conductive and nonconductive metal oxide particles, pigments, magnetic particles, biocide, and the like. The coating composition may also include a small amount of organic solvent, preferably the concentration of organic solvent is less than 1 percent by weight of the total coating composition. The invention does not preclude coating the desired polymeric material from a volatile organic solution or from a melt of the polymer.
The surface characteristics of the protective overcoat in the photographic element are in large part dependent upon the physical characteristics of the polymers which form the more or less continuous phase and the presence or absence of solid, nonfusible particles. However, the surface characteristics of the overcoat also can be modified by the conditions under which the surface is fused. For example, in contact fusing the surface characteristics of the fusing element that is used to fuse the polymers to form the continuous overcoat layer can be selected to impart a desired degree of smoothness, texture or pattern to the surface of the element. Thus, a highly smooth fusing element will give a glossy surface to the imaged element, a textured fusing element will give a matte or otherwise textured surface to the element, a patterned fusing element will apply a pattern to the surface of the element, etc.
Examples of coating aids include surfactants, viscosity modifiers and the like. Surfactants include any surface-active material that will lower the surface tension of the coating preparation sufficiently to prevent edge-withdrawal, repellencies, and other coating defects. These include alkyloxy- or alkylphenoxypolyether or polyglycidol derivatives and their sulfates, such as nonylphenoxypoly(glycidol) available from Olin Matheson Corporation or sodium octylphenoxypoly(ethyleneoxide) sulfate, organic sulfates or sulfonates, such as sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium bis(2-ethylhexyl)sulfosuccinate (Aerosol(trademark) OT), and alkylcarboxylate salts such as sodium decanoate.
Matte particles wellknown in the art may also be used in an overcoat composition. Matting agents have been described in Research Disclosure No. 308119, published December 1989, pages 1008 to 1009. When polymer matte particles are employed, the polymer may contain reactive functional groups capable of forming covalent bonds with the binder polymer by intermolecular crosslinking or by reaction with a crosslinking agent in order to promote improved adhesion of the matte particles to the coated layers. Suitable reactive functional groups include hydroxyl, carboxyl, carbodiimide, epoxide, aziridine, vinyl sulfone, sulfinic acid, active methylene, amino, amide, allyl, and the like.
In order to reduce the sliding friction of the photographic elements in accordance with this invention, the overcoat may contain fluorinated or siloxane-based components and/or the coating composition may also include lubricants or combinations of lubricants. Typical lubricants include (1) silicone based materials disclosed, for example, in U.S. Pat. Nos. 3,489,567, 3,080,317, 3,042,522, 4,004,927, and 4,047,958, and in British Patent Nos. 955,061 and 1,143,118; (2) higher fatty acids and derivatives, higher alcohols and derivatives, metal salts of higher fatty acids, higher fatty acid esters, higher fatty acid amides, polyhydric alcohol esters of higher fatty acids, etc., disclosed in U.S. Pat. Nos. 2,454,043; 2,732,305; 2,976,148; 3,206,311; 3,933,516; 2,588,765; 3,121,060; 3,502,473; 3,042,222; and 4,427,964, in British Patent Nos. 1,263,722; 1,198,387; 1,430,997; 1,466,304; 1,320,757; 1,320,565; and 1,320,756; and in German Patent Nos. 1,284,295 and 1,284,294; (3) liquid paraffin and paraffin or wax like materials such as carnauba wax, natural and synthetic waxes, petroleum waxes, mineral waxes, silicone-wax copolymers and the like; (4) perfluoro- or fluoro- or fluorochloro-containing materials, which include poly(tetrafluoroethylene), poly(trifluorochloroethylene), poly(vinylidene fluoride, poly(trifluorochloroethylene-co-vinyl chloride), poly(meth)acrylates or poly(meth)acrylamides containing perfluoroalkyl side groups, and the like. Lubricants useful in the present invention are described in further detail in Research Disclosure No.308119, published December 1989, page 1006.
An overcoat composition can be applied by any of a number of well known techniques, such as dip coating, rod coating, blade coating, air knife coating, gravure coating and reverse roll coating, extrusion coating, slide coating, curtain coating, and the like. After coating, the layer is generally dried by simple evaporation, which may be accelerated by known techniques such as convection heating. Known coating and drying methods are described in further detail in Research Disclosure No. 308119, Published December 1989, pages 1007 to 1008.
The photographic elements in which the images to be protected can contain conductive layers. Conductive layers can be incorporated into multilayer photographic elements in any of various configurations depending upon the requirements of the specific photographic element. Preferably, the conductive layer is present as a subbing or tie layer underlying a magnetic recording layer on the side of the support opposite the imaging layer(s). However, conductive layers can be overcoated with layers other than a transparent magnetic recording layer (e.g., abrasion-resistant backing layer, curl control layer, pelloid, etc.) in order to minimize the increase in the resistivity of the conductive layer after overcoating. Further, additional conductive layers also can be provided on the same side of the support as the imaging layer(s) or on both sides of the support. An optional conductive subbing layer can be applied either underlying or overlying a gelatin subbing layer containing an antihalation dye or pigment. Alternatively, both antihalation and antistatic functions can be combined in a single layer containing conductive particles, antihalation dye, and a binder. Such a hybrid layer is typically coated on the same side of the support as the sensitized emulsion layer. Additional optional layers can be present as well. An additional conductive layer can be used as an outermost layer of a photographic element, for example, as a protective layer overlying an image-forming layer. When a conductive layer is applied over a sensitized emulsion layer, it is not necessary to apply any intermediate layers such as barrier or adhesion-promoting layers between the conductive overcoat layer and the imaging layer(s), although they can optionally be present. Other addenda, such as polymer lattices to improve dimensional stability, hardeners or cross-linking agents, surfactants, matting agents, lubricants, and various other well-known additives can be present in any or all of the above mentioned layers.
Conductive layers underlying a transparent magnetic recording layer typically exhibit an internal resistivity of less than 1xc3x971010 ohms/square, preferably less than 1xc3x97109 ohms/square, and more preferably, less than 1xc3x97108 ohms/square.
Photographic elements of the invention differ widely in structure and composition. For example, the photographic elements vary greatly with regard to the type of support, the number and composition of the image-forming layers, and the number and types of auxiliary layers that are included in the elements. In particular, photographic elements can be still films, motion picture films, x-ray films, graphic arts films, paper prints microfiche, or small format films as described in Research Disclosure, Item 36230 (June 1994). Photographic elements can be either simple black-and-white or monochrome elements or multilayer and/or multicolor elements adapted for use in a negative-positive process or a reversal process. Generally, the photographic element is prepared by coating one side of the film support with one or more layers comprising a dispersion of silver halide crystals in an aqueous solution of gelatin and optionally one or more subbing layers. The coating process can be carried out on a continuously operating coating machine wherein a single layer or a plurality of layers are applied to the support. For multicolor elements, layers can be coated simultaneously on the composite film support as described in U.S. Pat. Nos. 2,761,791 and 3,508,947. Additional useful coating and drying procedures are described in Research Disclosure, Vol. 176, Item 17643 (December, 1978).
The photographic elements claimed in accordance with this invention are derived from silver halide photographic elements that can be black and white elements (for example, those which yield a silver image or those which yield a neutral tone image from a mixture of dye forming couplers), single color elements or multicolor elements. Multicolor elements typically contain dye image-forming units sensitive to each of the three primary regions of the spectrum. The imaged elements can be imaged elements which are viewed by transmission, such a negative film images, reversal film images and motion picture prints or they can be imaged elements that are viewed by reflection, such a paper prints. Because of the amount of handling that can occur with paper prints and motion picture prints, they are the preferred imaged photographic elements for use in this invention.
While a primary purpose of applying an overcoat to imaged photographic elements in accordance with this invention is to protect the element from reticulation and other physical damage, application of the overcoat may also protect the image from fading or yellowing. This is particularly true with elements that contain images that are susceptible to fading or yellowing due to the action of oxygen. For example, the fading of dyes derived from pyrazolone and pyrazoloazole couplers is believed to be caused, at least in part, by the presence of oxygen, so that the application of an overcoat which acts as a barrier to the passage of oxygen into the element will reduce such fading.
The photographic elements in which the images to be protected are formed can have the structures and components shown in Research Disclosures 37038 and 38957. Other structures which are useful in this invention are disclosed in commonly owned U.S. Ser. No. 09/299,395, filed Apr. 26, 1999 and U.S. Ser. No. 09/299,548, filed Apr. 26, 1999, incorporated in their entirety by reference. Specific photographic elements can be those shown on pages 96-98 of Research Disclosure 37038 as Color Paper Elements 1 and 2. A typical multicolor photographic element comprises a support bearing a cyan dye image-forming unit comprised of at least one red-sensitive silver halide emulsion layer having associated therewith at least one cyan dye-forming coupler, a magenta dye image-forming unit comprising at least one green-sensitive silver halide emulsion layer having associated therewith at least one magenta dye-forming coupler, and a yellow dye image-forming unit comprising at least one blue-sensitive silver halide emulsion layer having associated therewith at least one yellow dye-forming coupler.
As an example of a preferred dye-forming coupler, an xe2x80x9cNB couplerxe2x80x9d is capable of coupling with the developer 4-amino-3-methyl-N-ethyl-N-(2-methanesulfonamidoethyl) aniline sesquisulfate hydrate to form a dye for which the left bandwidth (LBW) of its absorption spectra upon xe2x80x9cspin coatingxe2x80x9d of a 3% w/v solution of the dye in di-n-butyl sebacate solvent is at least 5 nm. less than the LBW for a 3% w/v solution of the same dye in acetonitrile. The LBW of the spectral curve for a dye is the distance between the left side of the spectral curve and the wavelength of maximum absorption measured at a density of half the maximum.
The element can contain additional layers, such as filter layers, interlayers, overcoat layers, subbing layers, and the like. All of these can be coated on a support that can be transparent (for example, a film support) or reflective (for example, a paper support). Photographic elements claimed in accordance with the present invention may also include a magnetic recording material as described in Research Disclosure, Item 34390, November 1992, or a transparent magnetic recording layer such as a layer containing magnetic particles on the underside of a transparent support as described in U.S. Pat. No. 4,279,945 and U.S. Pat. No. 4,302,523.
Suitable silver halide emulsions and their preparation, as well as methods of chemical and spectral sensitization, are described in Sections I through V of Research Disclosures 37038 and 38957. Others are described in U.S. Ser. No. 09/299,395, filed Apr. 26, 1999 and U.S. Ser. No. 09/299,548, filed Apr. 26, 1999, which are incorporated in their entirety by reference herein. Color materials and development modifiers are described in Sections V through XX of Research Disclosures 37038 and 38957. Vehicles are described in Section II of Research Disclosures 37038 and 38957, and various additives such as brighteners, antifoggants, stabilizers, light absorbing and scattering materials, hardeners, coating aids, plasticizers, lubricants and matting agents are described in Sections VI through X and XI through XIV of Research Disclosures 37038 and 38957. Processing methods and agents are described in Sections XIX and XX of Research Disclosures 37038 and 38957, and methods of exposure are described in Section XVI of Research Disclosures 37038 and 38957.
Photographic elements can be imagewise exposed using a variety of techniques. Typically exposure is to light in the visible region of the spectrum, and typically is of a live image through a lens. Exposure can also be to a stored image (such as a computer stored image) by means of light emitting devices (such as LEDs, CRTs, etc.).
Images can be developed in photographic elements in any of a number of well known photographic processes utilizing any of a number of well known processing compositions, described, for example, in T. H. James, editor, The Theory of the Photographic Process, 4th Edition, Macmillan, New York, 1977. In the case of processing a color negative element, the element is treated with a color developer (that is one which will form the colored image dyes with the color couplers), and then usually with an oxidizer and a solvent to remove silver and silver halide. In the case of processing a color reversal element, the element is first treated with a black and white developer (that is, a developer which does not form colored dyes with the coupler compounds) followed by a treatment to render developable unexposed silver halide (usually chemical or light fogging), followed by treatment with a color developer. Development may be followed by bleach-fixing, to remove silver or silver halide, washing and drying. Newer types of film may eliminate some of the processing steps for the film, for example, if scanning is used to obtain the image information in electronic form prior to printing.

Imaged element with improved wet abrasion resistance